JP3024665B2 - Electric motor driven four-wheel steering system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor driven four-wheel steering system for controlling a rear wheel steering angle by an electric motor, and more particularly to a technique for detecting a motor lock.

[0002]

2. Description of the Related Art Conventionally, as an electric power steering apparatus using an electric motor, for example, Japanese Patent Application Laid-Open No. 1-266 has been disclosed.
No. 065 is known.

[0003] This conventional source discloses a technique in which when an actual current value to an electric motor is detected even though a command value is zero, a failure is determined and power supply to a motor drive circuit is cut off. .

[0004]

However, in the electric power steering apparatus described above, it is possible to detect a failure in a motor drive circuit which inputs a command value and converts the command value into an actual current value to the electric motor. Even if it is possible, it is not possible to detect that the electric motor itself is in a locked state due to the engagement of a gear or the like. In addition, in the case of an electric power steering device, the output from the electric motor is an assist force for the front wheel steering force, so that even if the actual current value to the electric motor is compared with the front wheel steering angle, the motor lock is detected. Can not do it.

On the other hand, in an electric motor-driven four-wheel steering system, when the electric motor is in a motor locked state due to a bite of a gear or a stuck rod, a high current is applied for a long time (for example, 10 seconds). If the motor is locked, it is required to detect the motor lock state without erroneous detection when the motor lock state occurs and before the motor burn-in occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an electric motor driven four-wheel steering device that controls a rear wheel steering angle by an electric motor, and that an incorrect motor lock state is obtained. It is to detect without detection and early.

[0007]

In order to solve the above-mentioned problems, in the electric motor-driven four-wheel steering system according to the present invention, a motor current that is higher than a set current value slightly lower than the maximum command current value flows through the electric motor. The motor lock monitoring detects that the motor is locked when the state in which the rear wheel steering angle does not fluctuate for a predetermined period of time that is longer than the time when the motor can run normally and is less than the motor burn-in time. Means were provided.

That is, as shown in the claim correspondence diagram of FIG. 1, an electric motor a for controlling a rear wheel steering angle by driving by applying a motor control current, and a motor current value actually flowing to the electric motor a Motor current value detecting means b to be detected
A rear wheel steering angle detecting means c for detecting a rear wheel steering angle; and a motor current value determining means d for determining whether the motor current value is equal to or larger than a set current value slightly lower than a maximum command current value. A rear wheel steering angle variation determining means e for determining whether there is a variation in the rear wheel steering angle, and a variation in the rear wheel steering angle despite the fact that a motor current greater than a set current value is flowing through the electric motor a. Motor lock monitoring means f for detecting that the motor is locked when the state where there is no motor continues for a predetermined time which is longer than the time during which the motor can run normally and less than the motor burn-in time.

[0009]

In the rear wheel steering angle control, the motor current value determining means d determines whether or not the motor current value is equal to or larger than a set current value slightly lower than the maximum command current value. In the angle variation determining means e, it is determined whether or not the rear wheel steering angle detected by the rear wheel steering angle detecting means c varies.

In the motor lock monitoring means f, the rear wheel steering angle is supplied to the electric motor a for controlling the rear wheel steering angle by driving the motor by applying the motor control current. If the state in which the motor does not fluctuate continues for a predetermined time that is equal to or longer than the time when the motor can run normally and less than the motor burn-in time, it is detected that the motor is locked.

Therefore, the motor current value, which is the current reference for determining the motor lock, is slightly lower than the maximum command current value.
As the motor current value is set to a low value, even when the normal electric motor a without lock abnormality is driven by a low current, the fluctuation of the rear wheel steering angle due to the road surface load is reduced. Erroneous detection of the motor lock can be prevented when there is no motor lock.

[0012] In addition, the duration of the state in which the rear wheel steering angle does not fluctuate despite the flow of the motor current, which is the time reference for the motor lock determination, is set to a predetermined time longer than the time during which the motor can run normally. Therefore, even in the case of a normal electric motor a having no lock abnormality, it is possible to prevent the erroneous detection of the motor lock when the vehicle satisfies the motor lock condition instantaneously, such as over a projection.

Further, since the duration of the state in which the rear wheel steering angle does not fluctuate even though the motor current, which is the time reference for the motor lock determination, is set to a predetermined time shorter than the motor burn-in time, the locked state is set. The motor lock state can be detected before motor burn-in of the electric motor a occurs.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

First, the configuration will be described.

FIG. 2 is an overall system diagram showing a vehicle to which the electric motor-driven four-wheel steering device according to the embodiment of the present invention is applied, and FIG. 3 is an electric rear wheel steering of the electric motor-driven four-wheel steering device according to the embodiment. FIG. 4 shows the mechanism, and FIG.
FIG. 2 is an electronic control system diagram centered on an S control unit.

In FIG. 2, 1 and 2 are front wheels, 3 and 4 are rear wheels, 5 is a mechanical front wheel steering mechanism, and 6 is an electric rear wheel steering mechanism.

The mechanical front wheel steering mechanism 5 increases a steering force input from a steering wheel 7 steered by a driver via a steering shaft 8 by a power steering (not shown), and increases the increased steering force to a rack shaft 9. Through the side rods 10 and 11 and the knuckle arms 12 and 13 to provide a steering angle to the front wheels 1 and 2.

The electric rear wheel steering mechanism 6 includes four
The rotational force of the high cas motor 15 (corresponding to the electric motor a) controlled by the motor output from the WS control unit 14 is transmitted to the worm 16 and the worm wheel 17.
And the rotational motion of the worm wheel 17 is converted into linear motion of the rack shaft 19 by meshing the gear portion of the pinion shaft 18 with the gear portion of the rack shaft 19, and the side rods 20, 21 and the knuckle arm are transferred from the rack shaft 19. Via the rear wheels 3,
4 to provide a steering angle.

The 4WS control unit 14 includes:
As shown in FIG. 4, the power supply circuit 14a and the sensor power supply circuit 1
4b, input interface 14c, CPU1, CPU
2, monitoring circuit 14d, D / A conversions 14e, 14f, 14
g, 14h, 14i, a CPU output monitoring circuit 14j, a relay output driver 14k, a motor output driver 14m, and a power steering solenoid output driver 14n.

The power supply circuit 14a includes a battery power supply directly from the battery 24 and an ignition switch 25.
The ignition power from is input.

The input interface 14c includes a sensor signal from a rear steering angle main sensor 26 (corresponding to a rear wheel steering angle detecting means c) and a rear steering angle subsensor 27 by a potentiometer, a sensor signal from a steering sensor 28, A sensor signal from the vehicle speed sensor 29 and switch signals from the stop lamp switch 30, the brake switch 31, and the inhibit switch 32 are input. Here, the rear steering angle main sensor 26 is a sensor that detects the rotation amount of the pinion shaft 18, and the rear steering angle sub-sensor 27 is a sensor that detects the stroke amount of the rack shaft 19.

The relay output driver 14k receives the monitoring output from the monitoring circuit 14d and the warning valve output from the warning valve 33, and
Sends a high cas relay output to

The motor output driver 14m is driven by a motor power supply via a high cas relay 34,
A rear wheel steering angle command is input from PU1 via D / A converters 14g and 14h, and a motor output is sent to the high cas motor 15.

The power steering solenoid output driver 14
n inputs a power steering command from the CPU 1 via the D / A converter 14i, and sends a power steering solenoid output to the power steering solenoid 35.

Next, the operation will be described.

[Motor Lock Monitoring Operation] FIG. 5 is a flowchart showing the flow of the motor lock monitoring operation performed by the monitoring circuit 14d of the 4WS control unit 14. Each step will be described below (corresponding to the motor lock monitoring means f). .

In step 50, the motor current value I is read.

The motor current value I is obtained by measuring the current actually flowing through the motor output driver 14m (corresponding to the motor current value detecting means b).

[0030] At step 51 (corresponding to the motor current value determining means d) of whether the motor current value I is set current value I ₀ or more is determined.

Here, the set current value I0 is set to 15A, which is slightly lower than the maximum command current value of 20A.

In step 52, when the condition of step 51 is satisfied, a rear wheel steering angle sensor value δrSEN is read from the rear steering angle main sensor 26.

In step 53, the sensor signal change amount Δδ
r is the currently read rear wheel steering angle sensor value δrSEN and 5 msec
It is calculated based on the difference between the previously read rear wheel steering angle sensor value δrSEN-5.

In step 54, it is determined whether or not the sensor signal change amount Δδr in step 53 is equal to or smaller than the set change amount K (corresponding to rear wheel steering angle change determination means e).

Here, the set change amount K depends on the side rod 2
Even if 0 and 21 are locked, there is fluctuation in the rear wheel steering angle due to backlash (max = 0.1 mm) due to the gear reduction mechanism or the like. Therefore,
0.1 mm = 0.033 ° is set. Since the rear wheel steering angle sensor value is obtained in the unit of mV, 60 mV obtained by converting 0.033 ° into mV is set change amount K.
As given.

In step 55, when the condition of step 54 is satisfied, a timer is started.

[0037] At step 56, whether the timer value T indicated by the timer is set timer value T ₀ or more is determined.

[0038] Here, setting the timer value T _0, the lock abnormality without normal HICAS motor 15 in a state that satisfies the motor lock condition even if the time, such as riding over projections considered are instantaneously (about 1 sec) As described above, when the motor current of 15 A or more is continuously applied to the high cast motor 15 in the locked state, the time (10
(about 2 sec), which is less than 2 sec. Even if the time is set as long as 2 seconds, the rear wheel steering angle does not change in the motor locked state, and there is no problem because there is no sudden change in vehicle behavior.

In step 57, if the time condition in step 56 is satisfied, it is determined that the motor lock is abnormal. Based on this abnormality determination, a fail-safe process of prohibiting rear wheel steering angle control and turning on the warning valve 33 is performed.

In step 58, the motor current value I is I in step 51 <If it is determined that I _0, or sensor signal variation Δδr is Δδr in step 54> If it is determined that K, the timer reset processing is performed It is.

In step 59, the high cas motor 15
Is determined to be in a normal state without a lock. Based on this determination, normal rear wheel steering angle control is performed.

[Normal state without motor lock] When the high-cass motor 15 is normal and does not satisfy the condition of I ≧ I ₀ , go to step 50 → step 51 → step 58 → step 59 in the flowchart of FIG. It is determined that the high-cass motor 15 is in a normal state without lock, and even if the condition of I ≧ I ₀ is satisfied, in the flowchart of FIG. 52 → Step 53 → Step 54 → Step 58 → Step 59
Then, it is determined that the high cas motor 15 is in a normal state without lock.

That is, if the motor current value condition of step 51 is satisfied, if the high cast motor 15 is normal, the high cast motor 1 based on the large motor current value I
Since the rear wheel steering angle greatly changes due to the drive of No. 5, the condition of step 54 is not satisfied, and it is determined that the high cas motor 15 is in a normal state without lock.

Accordingly, the motor current value I, which is the current reference for the motor lock determination, is set to a set current value I0 = 15 A, which is slightly lower than the maximum command current value of 20 A.
As in the case where the motor current value is set to a low value, even if the normal high-cass motor 15 having no lock abnormality is driven by a low current, the motor lock erroneous detection is performed when there is no change in the rear wheel steering angle due to the road surface load. Can be prevented.

[0045] when HICAS motor 15 [or the like riding over projections in normal without motor Lock is normal, at the time of riding over projections or the like, the condition of I ≧ I ₀ from the running resistance becomes momentarily excessive In some cases, the rear wheel steering angle hardly changes even though the motor current value I that satisfies the following condition is applied. In this case, in the flowchart of FIG.
The flow proceeds from step 53 → step 54 → step 55 → step 56. However, it is instantaneous to satisfy both the conditions of Steps 51 and 54. Therefore, the time condition of Step 56 is not satisfied.
4 does not satisfy the condition of the amount of change in the rear wheel steering angle, and in the flowchart of FIG.
The flow proceeds to step 52 → step 53 → step 54 → step 58 → step 59, and it is determined that the high cas motor 15 is in a normal state without lock.

Accordingly, the continuation time (set timer value T ₀ ) of the state in which the rear wheel steering angle does not fluctuate even though the motor current is flowing, which is the time reference for the motor lock determination, is
Since the time is 2 seconds which is longer than the time (about 1 second) that can be traveled when the motor is normal, even if the normal high-cass motor 15 has no lock abnormality, the condition that satisfies the motor lock condition may be momentarily considered. In this case, erroneous detection of the motor lock can be prevented.

[Motor Lock Abnormality] When the high cas motor 15 is in a locked state due to a biting of a gear, a stop of a rod or the like, and a motor current value I satisfying a condition of I ≧ I ₀ is flowing. Since there is no change in the rear wheel steering angle even though the motor current value I is flowing, in the flowchart of FIG.
The flow proceeds to step 52 → step 53 → step 54 → step 55 → step 56. This flow is repeated, and if the time condition of step 56 is satisfied, the flow proceeds to step 57 and it is determined that the high cas motor 15 has a lock abnormality. Is determined.

Therefore, the continuation time (set timer value T ₀ ) of the state where the rear wheel steering angle does not fluctuate even though the motor current which is the time reference for the motor lock determination is flowing,
Since the motor seizure time is set to 2 seconds, which is shorter than the motor seizure time (about 10 seconds), the motor lock state can be detected before the motor seizure of the locked highcast motor 15 occurs. Burn-in of the motor 15 can be prevented.

Next, the effects will be described.

(1) In an electric motor-driven four-wheel steering system in which the rear wheel steering angle is controlled by the high-cass motor 15,
For the maximum command current value of 20 A for the HiCass motor 15
A state in which the rear wheel steering angle does not fluctuate even though a motor current of a slightly lower set current value 15A or more is flowing for more than 2 seconds which is longer than the time when the motor can run normally and less than the motor burn-in time. Since the apparatus performs the motor lock monitoring logic processing for detecting the motor lock state, the motor lock state can be detected early without any erroneous detection.

(2) The set change amount K of the sensor signal change amount Δδr, which is a criterion for determining whether or not there is a rear wheel steering angle change,
The maximum value of the play is given in consideration of the play (max = 0.1 mm) due to the gear reduction mechanism or the like, so that it is possible to prevent erroneous detection in a normal state when the play is set to be larger than the maximum value of the play. In addition, it is possible to prevent erroneous detection at the time of lock abnormality when the value is set smaller than the maximum value of the play.

Although the embodiment has been described with reference to the drawings, the specific configuration is not limited to the embodiment, and any changes or additions without departing from the gist of the present invention are included in the present invention. It is.

For example, the set current value I ₀ (15 A), the set timer value T ₀ (2 sec), and the set change amount K (60 mV) are not limited to the values of the embodiment, but are controlled by a control system or a system mounted. Can be set appropriately depending on the vehicle.

[0054]

As described above, according to the present invention, in an electric motor-driven four-wheel steering system in which a rear wheel steering angle is controlled by an electric motor, the electric motor is slightly lower than the maximum command current value. If the state in which the rear wheel steering angle does not fluctuate even though the motor current that is equal to or greater than the set current value flows continues for a predetermined time that is longer than the time when the motor can run normally and less than the motor burn-in time, Since the motor lock monitoring means for detecting the locked state is provided, it is possible to obtain an effect that the motor locked state can be detected early without any erroneous detection.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to a claim showing an electric motor-driven four-wheel steering device of the present invention.

FIG. 2 is an overall system diagram showing a vehicle to which the electric motor-driven four-wheel steering device according to the embodiment of the present invention is applied.

FIG. 3 is a diagram showing an electric rear wheel steering mechanism of the electric motor driven four-wheel steering device of the embodiment.

FIG. 4 is an electronic control system diagram centering on a 4WS control unit of the embodiment apparatus.

FIG. 5 is a flowchart illustrating a flow of a motor lock monitoring operation performed by a monitoring circuit of a 4WS control unit of the embodiment device.

[Explanation of symbols]

 a electric motor b motor current value detecting means c rear wheel steering angle detecting means d motor current value determining means e rear wheel steering angle fluctuation determining means f motor lock monitoring means

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ identification code FI B62D 113: 00 (58) Field surveyed (Int.Cl. ⁷ , DB name) B62D 5/04 B62D 6/00 B62D 7/14

Claims (1)

(57) [Claims] 1. An electric motor for controlling a rear wheel steering angle by driving by applying a motor control current, a motor current value detecting means for detecting a motor current value actually flowing to the electric motor, a rear wheel steering angle. Rear wheel steering angle detecting means for detecting whether or not the motor current value is equal to or greater than a set current value slightly lower than the maximum command current value; and A rear wheel steering angle variation determining means for determining whether there is a variation in the steering angle, and a state in which there is no variation in the rear wheel steering angle even though a motor current equal to or greater than a set current value flows through the electric motor, Motor lock monitoring means for detecting that the motor is in a locked state when the motor continues to run for a predetermined period of time that is longer than the time during which the motor can run normally and less than the motor burn-in time. Four-wheel steering .